# CVE-2025-26466: Openssh: denial-of-service in openssh > A malicious client can cause OpenSSH server memory exhaustion by sending excessive ping packets, leading to denial of service. - **Severity:** Medium 5.9 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H`) - **Exploited in the wild:** Not known - **Login needed:** Not needed - **Attackable:** Over the internet - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 28 Feb 2025 - **Updated:** 21 Oct 2026 - **Also known as:** ALPINE-CVE-2025-26466, AZL-56898, BELL-CVE-2025-26466, DEBIAN-CVE-2025-26466, GHSA-m92w-x6j2-5gc5, RHBA-2025:6305, UBUNTU-CVE-2025-26466 ## What is CVE-2025-26466? CVE-2025-26466 is a medium-severity denial of service vulnerability in Canonical Ubuntu Linux, published on 28 Feb 2025. An attacker can exploit it over the internet without logging in, with no action from the victim. ### Official description A flaw was found in the OpenSSH package. For each ping packet the SSH server receives, a pong packet is allocated in a memory buffer and stored in a queue of packages. It is only freed when the server/client key exchange has finished. A malicious client may keep sending such packages, leading to an uncontrolled increase in memory consumption on the server side. Consequently, the server may become unavailable, resulting in a denial of service attack. Weakness: CWE-770 (Allocation of Resources Without Limits or Throttling) ## Which versions are affected by CVE-2025-26466? It affects 3 products. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `openssh` | Red Hat:enterprise_linux:10.0 | All versions | 0:9.9p1-7.el10_0 | | `openssh-askpass` | Red Hat:enterprise_linux:10.0 | All versions | 0:9.9p1-7.el10_0 | | `openssh-askpass-debuginfo` | Red Hat:enterprise_linux:10.0 | All versions | 0:9.9p1-7.el10_0 | | `openssh-clients` | Red Hat:enterprise_linux:10.0 | All versions | 0:9.9p1-7.el10_0 | | `openssh-clients-debuginfo` | Red Hat:enterprise_linux:10.0 | All versions | 0:9.9p1-7.el10_0 | | `openssh-debuginfo` | Red Hat:enterprise_linux:10.0 | All versions | 0:9.9p1-7.el10_0 | | `openssh-debugsource` | Red Hat:enterprise_linux:10.0 | All versions | 0:9.9p1-7.el10_0 | | `openssh-keycat` | Red Hat:enterprise_linux:10.0 | All versions | 0:9.9p1-7.el10_0 | | `openssh-keycat-debuginfo` | Red Hat:enterprise_linux:10.0 | All versions | 0:9.9p1-7.el10_0 | | `openssh-keysign` | Red Hat:enterprise_linux:10.0 | All versions | 0:9.9p1-7.el10_0 | | `openssh-keysign-debuginfo` | Red Hat:enterprise_linux:10.0 | All versions | 0:9.9p1-7.el10_0 | | `openssh-server` | Red Hat:enterprise_linux:10.0 | All versions | 0:9.9p1-7.el10_0 | | `openssh-server-debuginfo` | Red Hat:enterprise_linux:10.0 | All versions | 0:9.9p1-7.el10_0 | | `openssh-sk-dummy-debuginfo` | Red Hat:enterprise_linux:10.0 | All versions | 0:9.9p1-7.el10_0 | Products: Canonical Ubuntu Linux, Debian Debian Linux, OpenSSH. ## How do I fix CVE-2025-26466? Apply the vendor's patch. ## Is CVE-2025-26466 being exploited? It is not confirmed as exploited in the wild, but public exploit code for CVE-2025-26466 exists. Public exploit code: - The OpenSSH client and server are vulnerable to a pre-authentication DoS attack between versions 9.5p1 to 9.9p1 (inclusive) that causes memory and CPU consumption (github_poc): https://github.com/rxerium/CVE-2025-26466 - CVE-2025-26466 - SSH Ping DoS Ruby module for Metasploit Framework (github_poc): https://github.com/mrowkoob/CVE-2025-26466-msf - poc for CVE-2025-26466 (github_poc): https://github.com/tpirate/CVE-2025-26466 - CVE-2025-26466 OpenSSH SSH2_MSG_PING DoS PoC (github_poc): https://github.com/acidboonrs/cve-2025-26466-openssh-poc - https://github.com/K0n9-log/cve-2025-26466-canvas (github_poc): https://github.com/K0n9-log/cve-2025-26466-canvas ## Other vulnerabilities in Canonical Ubuntu Linux - [CVE-2020-11651](https://insights.sbomify.com/CVE-2020-11651/): SaltStack Salt Authentication Bypass (critical 9.8, exploited in the wild) - [CVE-2020-7247](https://insights.sbomify.com/CVE-2020-7247/): OpenSMTPD Remote Code Execution (critical 9.8, exploited in the wild) - [CVE-2019-16928](https://insights.sbomify.com/CVE-2019-16928/): Exim Out-of-bounds Write (critical 9.8, exploited in the wild) - [CVE-2018-6789](https://insights.sbomify.com/CVE-2018-6789/): Exim Buffer Overflow (critical 9.8, exploited in the wild) - [CVE-2015-2590](https://insights.sbomify.com/CVE-2015-2590/): Oracle Java SE and Java SE Embedded Remote Code Execution (critical 9.8, exploited in the wild) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2025-26466 and fix it if it is affected. What it is: CVE-2025-26466 is a medium-severity denial of service vulnerability in Canonical Ubuntu Linux, published on 28 Feb 2025. An attacker can exploit it over the internet without logging in, with no action from the victim. Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2025-26466 exists. Affected product: Canonical Ubuntu Linux. No package-level version data is available, so check the vendor advisory linked from the reference page. Task: 1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies. 2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it. 3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead. 4. Run the tests and summarise what changed and why. 5. If nothing in the project is affected, say so and change nothing. Reference: https://insights.sbomify.com/CVE-2025-26466/ (Markdown: https://insights.sbomify.com/CVE-2025-26466/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2025-26466 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-26466 - OSV: https://osv.dev/vulnerability/CVE-2025-26466 --- From sbomify Insights: https://insights.sbomify.com/CVE-2025-26466/ Summaries are generated and may contain mistakes; the official description above is the record.